Audi (EU) A6, S6, RS6 4B A6 1.8 20V Turbo quattro (1997-2000)

Which oil should you use for your Audi (EU) A6, S6, RS6 4B A6 1.8 20V Turbo quattro (1997-2000)? Complete advice for all components, such as the engine, gearbox (transaxle), brake system, power steering system and cooling system.